Fuel cell oxygen cathode with Nafion and platinum: the effect of active layer heating on overall cathode characteristics

Abstract

A fuel cell with Nafion and platinum is considered. The effect of heating of the oxygen cathode active layer on the cathode overall characteristics (current and power density) is taken into account for the first time. Attention is focused on calculations of Tafel plots of oxygen cathodes and also on how the active layer temperature changes with the potential. Calculation parameters are as follows: fuel cell initial temperature, cathode active layer thickness, gas-diffusion layer effective heat conductivity and thickness. The following conditions of cathode operation are studied: (1) heat formed in the cathode active layer is almost completely removed, no active layer heating is observed, the active-layer temperature remains equal to that of fuel cell operation; (2) heat removal is impeded, the heat conductivity of the gas-diffusion layer is insufficiently high to remove heat. In the latter case, the active layer temperature may increase by several tens of degrees. A fundamental difference of Tafel plots for the catalytic layers studied in model experiments and the cathodic active layers is demonstrated. In the latter case, the first Tafel plot segment may extend further up to potentials of ∼0.6 V.